Black and white cookies

Whisk the flour, baking soda, baking powder and kosher salt together and preheat the oven to 350F.

Cream the room temperature butter with the granulated sugar until very pale, light and fluffy, about four minutes with a hand mixer or two to three in a stand mixer, scraping down partway.

Beat in the eggs one at a time, then the vanilla.

Add the dry and wet alternately, beginning and ending with dry: three additions of flour and two of buttermilk, mixing only on low and stopping while a little flour still shows.

Finish by hand with a spatula, scraping the sides and bottom, so no part is more buttery than another.

Portion into two ounce scoops, about a quarter cup each, onto a plate or parchment lined tray without shaping them.

Chill 20 to 25 minutes until the butter firms up enough to roll them into spheres, keeping the rest covered in the fridge.

With lightly floured hands roll six portions into spheres, space them on a baking sheet and flatten them slightly to about three quarters of an inch tall.

Bake in the centre of the oven until the centres are matte and springy to the touch and they are still very pale, with maybe a little gold at the edge. Baking time is never stated.

While still very hot, set a large circular cutter over each cookie and move it in little circles to make it perfectly round.

Cool on the sheet long enough that they do not take grooves from the rack, then cool completely upside down.

For the icing, whisk the milk, corn syrup, vanilla, pinch of salt and two tablespoons of boiling water into the confectioners sugar gently at first, to a thick, pourable, ribbony consistency.

With a small offset spatula draw the icing up and let it run down the middle of the cookie in a line, then fill in half the cookie out to the edge in an opaque layer. If it runs off the edge add powdered sugar; if too thick add tap water half a teaspoon at a time.

Whisk the cocoa powder into the remaining vanilla icing, thinning with a little tap water, until it falls fluidly off the whisk but still leaves a ribbon on the surface.

Ice the other half of each cookie with the chocolate, following the line already laid, handling them carefully so the set vanilla does not crack.